Reducing congestion on the highways has been a goal for many years. One possible solution is to make existing highways more efficient through automation. To be safe and effective, however, automated highways require some means for maintaining optimum distance between vehicles. This requires measuring distances between vehicles and establishing communication links between vehicles and the highway and/or among vehicles traveling on the highway.
Measuring and maintaining distances between vehicles on an automated highway, such as the proposed Intelligent Vehicle Highway System (IVHS), is complicated by the clutter of unwanted information from the environment that is continually received by the sensor system. Provisions must be made for system calibration, changing weather, vehicles entering and exiting the highway, and numerous other obstacles that might be encountered. Various systems, including those employing active sensors, such as those based on mm wave radar, laser radar, and sonar, or passive systems, such as those based on stereo vision, have been proposed for measuring distance between vehicles on automated highways. The known systems, however, have high cost factors and/or technical problems that have not been overcome. Given the foregoing constraints and the desire to develop automated highways, there is a clear need for an effective system for measuring and maintaining distance between automotive vehicles that performs safely and efficiently at a satisfactory level of cost.